function download(){
var x=(screen.width-313)/2;
var y=(screen.height-437)/2;

var o=open("logo.htm","","resizable=no,width=313, height=437,menubar=no,statusbar=no,toolbar=no");
o.moveTo(x,y);
}
function cover_book(){
var x=(screen.width-380)/2;
var y=(screen.height-560)/2;

var o=open("book_cover.htm","","resizable=no,width=380, height=560,menubar=no,statusbar=no,toolbar=no");
o.moveTo(x,y);
}
function structure(){
var x=(screen.width-800)/2;
var y=(screen.height-600)/2;

var s=open("Structure1.htm","","resizable=yes,width=800, height=600,menubar=no,statusbar=no,toolbar=no,scrollbars=yes");
s.moveTo(x,y);
}
function certificate(){
var x=(screen.width-571)/2;
var y=(screen.height-415)/2;

var s=open("certificate.htm","","resizable=no,width=571, height=415,menubar=no,statusbar=no,toolbar=no,scrollbars=yes");
s.moveTo(x,y);
}